Concrete expansion joint



Oct. 26, 1948.

\ Filed Sept. '7, 1944 CONCRETE EXPANSION JOINT J. N. HELTZEL 4Sheets-Sheet l Oct. 26, 1948. J. N. Hx-:LTzEL CONCRETE EXPANSION JOINTFiled Sept. 7, 1944 4 Sheets-Sheet 2 9 Humm gime/wm Oct. 26, 1948. J, N,HELTZEL 2,452,462

CONGRETE EXPANSION JOINT 'iled Sep. 7, 1944 v 4 Sheets-Sheet 5 3mm lOct. 26, 1948. J, N, HELTZEL I 2,452,462

' CONCRETE EXPANSION JOINT Filed Sept. '7, 1944 4 Sheets-Sheet 4Patented ct. 26, i948 UNITED STATES PATENT Fries CONCRETE EXPANSIONJOINT John N. Heltzel, Warren, hi Y Application September 7, 1944,Serial No. 553`,05'

2 Claims. 1

This invention relates to dowel means for concrete expansion joints, orcontraction joints.

'I'he invention is more particularly concerned with improved dowel meansfor expansion joints as provided between concrete or similar slabs orsections of roadways, floors, airfield runways, Walls, and the like, forpermitting relative horizontal movement of the slabs, while preventingthe same from shifting laterally and vertically of their planes; and theVpresent application is a continuation in part of my copendingapplication Serial N-o. 313,128, Patent No. 2,358,328, led January 9,1940,

Modern traffic conditions on highways and airfield runways havenecessitated an increased use of load transfer members bridging joints,both longitudinal or transverse, between the opposed edges of adjacentconcrete slabs. Experience has shown that the problem is not solved bythe mere addition of load transfer dowels, such as commonly employed,for the shrinkage of plastic concrete when drying sets up a frictionaldrag on the embedded dowel bars, with the consequent breaking of theconcrete at points remote from the joints between the slabs. It has beenfound, also, that where dowel bars alone are depended upon, there is aninevitable warping of the concrete slabs which tends to bend the dowelbars. This .bending prevents restoration of the slabs to their initialcondition on the subgrade and in addition, there is a constant breakingaway of concrete or falling off of the material at the faces of theconcrete slabs in the areas surrounding and adjacent to the dowel bars.

The tendency of adjacent concrete slabs and the joints between the slabsto shift under changing atmospheric conditions as well as under theincessant loadsfpassing thereover has long been recognized, and theprovision of efficient load transfer means at such joints has attractedthe skill of engineers in many fields as well as steel and concretecontractors, and as a result many varieties of load transfer means inthe form of dowels bridging concrete slab joint have been proposed andused.

In the use of such load transfer dowels, it is necessary of course thatexpansion and contrac- -tiori of the joint be permitted as a result ofwhich,

the dowels must have relative movement to one of the slabs adjacent ajoint in a direction axially of the dowels, and it is also essentialthat the dowels have relatively no movement transverse of their axes. i

It lhas been found that dowels in use with as to remain rigid therewithunder all conditions of use, and that such united dowels be conf-ined tovaxial movement only relatively to another slab.

It has als-o been found that for maximum efliciency the load bearingmembers or dowel structures should be so constructed and arranged as tobe balanced on opposite sides of the joint and that the dowel portionsspanning the joint should have a maximum load bearing and transferringcapacity vertically through the dowel.

It is a primary object of the invention, therefore, to provide dowelmeans for concrete expansion joints and the like which satisfy the abovenoted requirements in providing load transfer connections of maximumstrength and eiciency.

An object of the present invention, therefore, is to provide improvedmeans for producing joints in concrete roads and the like, utilizingdual dowel means in association with dual supporting shear plates, inwhich friction with respect to the surrounding concrete is reduced to aminimum by the novel bridging structure of balanced down and bearingmembers.

Another object is to provide, in such joints, means to eliminate`tension in the concrete itself and to confine such tension directly anduniformly to the dowel and shear plate means constituting the loadtransfer elements extending in balanced relation between the respectiveslabs.

A still further object is to provide a dual dowel assembly concrete slabin a joint installation fo-r transferring vertical load strain to thedowel means at the joint by the employment of cooperating dual shearplates associated with the concrete slabs and dowels..

A further object of the invention is the provision of dowel Ameans. forconcrete expansion joints including a dowel and dowel shear plate andsocket arranged for rigid connection with each slab adjacent a jointtherebetween with pro-- vision for each dowel to telescopically engagewithin a socket in the expansion and contraction of the joint.

A still further object of the invention is the provision of a dowel unitfor use in concrete expansion joints comprising a pair of shear plates,each having a dowel and dowel socket rigid therewith, each shear platehaving an aperture for confining the dowel of the other shear plate toaxial movement in expansion or contraction of the connected concreteslabs, and each shear plate 'having means rigid therewith fortransmitting 3 joints including elements for cooperation at oppositesides of the joint and which elements are of like construction wherebymanufacture and the setting up of the dow'el means is simplified to anotable extent. g y

A still. further object of the invention isy the provision of dowelmeans for concrete expansion joints wherein the joint is greatlystrengthened and bal-anced at each side thereof.

With the above and other objects in view, which will become more fullyapparent as the nature of the invention is better understood, the 'samecon;- sists in the novel features of construction, corn-` bination andarrangement of parts as will be hereinafter more fully described,illustrated 4and claimed in the accoinpanyingdrawings.

In the drawings, wherein like characters of reference Vdenotecorresponding parts in related views:

Figure l is a perspective view disclosing a pair of cooperating shearplates, `each provided with a dowel, the plates being in separated andalined relation with the doweis positioned for entry through an openingin an expansion joint strip thence into an` alin'ed socket in theopposed shear plate; 1

Fig. 2 i's a top. plan' view,y partially in section, of the; structureof Fig. l in assembled position;

Fig: 3 is a vertical longitudinal section, showing the structure of Fig.l operatively positioned adj acent the joint between a pair of concreteslabs;

Fig. 4v is a perspective view simil-ar to Fig. 1 showing modified forms.of; shear plates and dowels;

Fig, 5-is a perspective view showingA the separated elements of Fig. 4in assembledY position;

Fig. 6` is a diagrammatic. View in side elevation showing theeffectiveness of the structure of Figs. #i and 5 at the joint betweenl apair of concrete siabs; i 1 i Fig. '7 is: also a diagrammatic viewshowing the WellI known jacleknilng of the concrete slab joints in theabsence of effective load' transferring and reinforcingmeans; f

Fig. 8 is a sectional perspective View disclosing a further embodimentofthe invention;

Fig. 9, is an enlarged transverse sectional view substantially in theplane of line 9 9, Fig. 8;

Fig. le() is a perspective View of a still further embodiment of theinvention;

Fig. 1l is a 'horizontal sectional view on a reduced scale, as observedin. the plane of line I-I--IIeLFigt 10;

Fig. 1-2 isfa .perspective viewv of .a still further embodiment of thelinvention;

Fig. 13 is a perspective view of a still further flrs't to Figs. 1 'to3, wherein-is disclosed.' a dualA i doivel reinforcing and loadtransferring-structure for use at the joints` of concrete slabs andwhich structure` is symbolic of ail the modifications di's' closed', thestructure, as shown includes a pair of cooperating unitary elements II)which are VIof i assaiez horizontal thickness extends through theaperture l2 in each plate Il at one side thereof and is rigidly securedto the plate as by welding, indicated at I4.

Each barwI3 Mincludes a relatively long end port-ion` I5` for projectioninto the body of the concrete slab remote from the shear plate andjoint, as shown in Fig. 3, and an opposite end portion which constitutesthe dowel portion I6.

The apertures I2 are of a transverse Width equal to double the thicknessof the respective bars |13l such that when the elements IU areoperatively positioned an aperture of the size of each dowel l5 will beprovided in each plate I I adjacent the bar I3 which is rigidly securedthereto. The dowel portions I6 will thus lap each other when assembledyand slide into the respective apertures I2 upon moving'theshear plates II into operative positions, as in Figs. 2 and3.

A dowel socket or housing I1 must be provided in each concrete slab forslidably receiving each dowel I6 and such socket is preferably formed bymea-ns of a sheet of thin metal bent into rectangular form and one sidehaving its opposed edges welded as at I8 to the top and bottom faces ofthe bar i3. As best shown at the extreme left of Fig. 1 the vertical webof the sheet metal housing -is of greater length then the top and bottomfaces so as to be bent therebetween and-welded at 2d into engagementwith the bar I3. These sockets or housings I'I are therefore closedexcept for the Vdowcl entrance I-Z in the shear plate whereby admissionof concrete is avoided for free relative sliding of the dowels I6 duringexpansion or contraction of the concrete slabs S (Fig. 3).

The usual expansion joint sealing strip 22 is provided with arectangular openingk 23 adjacent each plate and 'dowel structure forreceiving the relatively slidable dcwels I6 as is clearly indicated inFigs. 2 and 3.

The rear end of the bar portions I5 extend well into the concrete vslabsS at Vopposite sides of the joint between two slabs and function toanchor the'dow-els and distribute the stresses therein and to transmitstrains remote from the joint directly tothe .shear plates in theopposed faces of the slabs.

The 'dual dowel structure herein disclosed in -higlfily'efiicient forthispurpose and overcomes the ineffectiveness of dowel structuresheretofore used or proposed. It is here to be particularly noted thatwhile each dowel llli s freely movable in the socket I 'I ofthecooperating dowel, said dowelsare rigdlyvsupported by its vrespectiveshear plate ll.

'The'dowels are positioned flatw-ise against each other or inlaterally-contacting relation to mutufally support eachother when theslabs contract or expand. Under this condition the dowels will 'slide inopposing directions, -each dowel bearing 'on the-shear plate "of theother dowel, and the pair of dowels cooperating to dorm 'a double -trussspanning the j'oint at 'required intervals .bet-Ween the 'concreteslabs.

As disclosed, the pr'esent `structure provides a pair vof unitary rigidelements each embodying van 'anchoring portion, a shear plate, a dowel,'and a vldowe'l receiving socket, and leach said element willbe'rigidlyembedded in Ian vedge -or 'end face of a concrete slab asindicated in Fig. 3. rThus, thecoaction of both elements Yorunits, whichmay be identical, will result yinthe most efficient and rigidf'or'in of`doweli'ng,"and one iwhich will prevent jackikning of the :slab asindicated diagrammatically in Fig` 7, with ample #provision Ahowever'f-for. t'h'e :free .longitudinal movement fof the dowels within thesockets and within the shear plates to permit the slabs to expand or tocontract.

It is further to be noted that by the improved structure hereindisclosed a balanced effect is provided on both slab ends of andadjacent a joint therebetween which is necessary for continued operationof a dowel as a supporting element and for the efficient action hereindescribed. This is not found in other structures of this generalcharacter heretofore used or proposed.

Referring nowfto Figs. 4 and 5 wherein is illustrated a structuresimilar to that of Figs. 1, 2 and 3, the shear plates are provided withupper and lower flanges 25 and 26 for anchorage in the concrete slabswhereby holding the shear plates eiectively in position. Their upperanges 25 are preferably provided with openings 21 to permit concrete toiiowabout the structure and honeycombing of the plastic material. Theopenings 21 further functionlto more rmly unite the flanges with theconcrete. The bar portions I5 in this embodiment are'provided withlaterally deflected rear end portions 28 for the purpose of greateranchorage in the concrete body of a slab as well as stress-relieving.

AIn the embodiment of the invention the bar portions |59' are providedwith openings 29 for receiving a wirefsupport 30. The support maycomprise opposed portions 3| each having a linear subgrade engagingportion provided with an angle portion 32 to permit contraction andexpansion of the slabs. The support is primarily adapted to maintain thestructure above the sub-grade and when it is desired to elevate thestructure to a higher position, the portions 3| are brought closer andwhen it is desired to lower the structure, the

portions 3| are spread apart. In this manner the assembly may be'`supported in a variable position above the sub-grade. Otherwise thestructure is the same as that of Figs. 1 to 3 and functions insubstantially the same cooperative manner.

In Fig. 6 is diagrammatically illustrated the structure of Figs'.` 4 and5 in operative association with a concrete slab joint, but it is,however, to be understood that the dual dowel structures of the otherembodiments of the invention will provide substantially the sameeiiiciency. The slabs S as indicated are maintained in alinement whenthe improved plate and dowel structure are inoorporated in the joint dueto the long strain transmitting bar portions |55, the dual truss dowels,and thebalanced support at each side of the joint.

When, however, ordinary structures of a dowel and socket embedded in theopposed end of the slabs is utilized at the joint, as heretoforeproposed, insufiicient support and balanced relation is provided so thatthe slabs S will jack-knife as indicated in Fig. 7 and thereafterprevent operation of the parts as a supporting bridge.

A further embodiment of the invention is illustrated in Figs. 8 and 9which show the same general organization as previously described. Theshear plates ||b are provided with upper and lower right angular flanges35 and 36 respectively, and the upper flanges 35 are each provided withan aperture 31. In this embodiment the usual expansion joint strip 22 issupported or held with its openings 23 in registration with the aperturel2 by a removable cap strip 38 which is of inverted U-shape. This capstrip as shown is provided with prongs 39 in registry with the apertures31 and for entering same as indicated. This also temporarily preventsseparation of the shearV plates from the strip 22 after setting up ofthe parts. v l

- In this embodiment the bar portions |5b are provided with downwardlyprojectingsupports 4|) for engagement with the sub-grade. l Suchsupports are of a length to support the joint strip 22 on the sub-grade,or if desired in a suspended position. The cap strip 38 is removed priorto the final nishing of' the concrete slabs. A wire spring member 4| mayextend between the supports 40 to aid in holding the shear platesagainst the joint strip. However, when the cap strip 38 is used, suchspring member may be omitted. The bar portions I5b may further beprovided with upwardly diverted anchorage portions 42 for better unitingthe bars with the concrete slabs. l

' A further embodiment of the invention is illustrated in Figs. 10 and11, whereinthe shear plates ||c are each provided with a pair ofadjacent horizontally spaced vertically elongated apertures 44 and 45,and the bars providing the dowels |6 are each formed into a U-shapedconcrete anchorage portion 46. One leg of each U-shaped portion 46 isextended to'provide the dowel `which extends forwardly through theaperture 44, and the other leg terminates at the rearside of the shearplate laterally of but adjacent the aperture 45. These legs' of theU-shape'd flat bar portions 46 are secured to the shear plates as bywelding at the point of contact therewith as at 41 and 48. Cover plates49 and 50 may be secured as by welding or otherwise to the upper andlower edges of the U-shaped bar portions 46 so as to formfenclosedpockets, as indicated at the left in Fig. 10, thereby providingunobstructed dowel receiving sockets |1.

4l *A further embodiment of the invention is illustrated in Fig. 12which, as in all embodiments, comprises shear plates |d each havingrigidly secured thereto in horizontally spaced relation a dowel |6and adowel socket I1". 'Each shear plate of this embodiment is provided withan integral laterally and inwardly directed iiange which seats on thesub-grade and which is returned upon itself in the form of a secondsuperposed flange 53. A relatively flxedbase is thus provided whichextends up into the concrete slab with which the plate is associated.The shear plates are provided with anchoring and strain transmittingmembers 54 which extend upwardly in continuation of the'dowels Hifi.'`The upper edges of the shear plates are provided with flanges 55 whichare ribbed as at 56 for stiffening the ilange and providing betteranchorage in the concrete slabs. The shear plates may further beprovided with reinforcing and anchoring ribs 51 between the flanges.

A further embodiment of the invention is illustrated in Fig. 13 which issubstantially of the form of Figs. 1 to 3 but wherein the bars are ofI-beam form or construction. In this embodiment, the shear plates ||eare each provided with a relatively large centrally disposed rectangularaperture 59 through which extends an I-beam shaped bar 6D welded to theplate at the margin of the aperture as at 6|. The width of the aperturesprovidesv for sliding contact between` adjacent anges of the bars inmovement of the dowels ||ib through the apertures and into the socketsI1. These shear plates ||e are shown provided with upper and lowerflanges 62 and 63, each ofwhich is further provided with an angularlydisposed anchoring tongue 64. The anges 62 and 63 are

